This invention generally relates to a portable direct current power supply for a handheld electronic device. More particularly, this invention pertains to a direct current power supply for devices such as cellular phones.
The proliferation of portable battery powered devices, such as cellular telephones, has increased dramatically in the last several years and this trend is expected to continue. The phones typically use a rechargeable battery that is built into the phone to provide the needed power. The length of time that the battery powers the phone is dependent primarily upon the size of the battery and the number of energy consuming features built into the phone. In response to consumer demand, cell phone manufacturers incorporate into the phones features such as the ability to send and receive digital pictures and/or text messages. Unfortunately, the inclusion of these features usually places additional demands on the rechargeable batteries that power the cell phones. The net result is that the cell phones' run times become shorter and shorter due to the increased power demands. At the same time that the electrical demand placed on the battery is increasing, the size and weight of cell phones is decreasing in order to reduce the size of the phones. As the size of the cell phone is reduced, the size of the battery compartment built into the cell phone is also reduced. The existence of these two trends (i.e. increased electrical demand and reduced battery size) has caused many cell phone users to experience a failed telephone call or data transmission due to the depletion of their phone's battery at an inopportune moment. An additional trend that complicates resolving this problem is that most cell phones require a battery that has specific size and shape characteristics. In order to encourage consumers to purchase replacement batteries from the cell phone manufacturer, the cell phones are made with batteries that have unique shapes, locking mechanisms, voltage requirements, etc. Furthermore, the recharging port built into the cell phones limit the type of charger that can be connected to the cell phone. Collectively, these factors limit the consumer's ability to rapidly replace the depleted battery with another power supply.
Numerous attempts have been made to develop a suitable portable power supply for cellular telephones. For example, U.S. Pat. No. 6,127,801 discloses a power supply that includes a battery pack and a base unit which has bidirectional circuitry. The battery pack is made to snap into the base unit which is designed to be clipped onto the cellular telephone. Unfortunately, the battery pack and base unit tend to increase the size and weight of the cell phone, which is contrary to the consumer's desire, while also causing additional proliferation in the number of components the consumer needs to replace when the phone's battery is depleted. In another example, U.S. Pat. No. 6,709,784 discloses a unique battery pack that can be plugged into a cellular phone's contact to recharge the phone's built-in rechargeable battery and/or directly power the cell phone. This invention bundles the battery with the plug that allows the battery pack to be connected to the phone. Consequently, when the battery pack's battery is depleted the entire battery pack, including the plug, must be discarded which increases the consumer's cost.
Therefore, there exists a need for a portable direct current power supply that uses a commonly available battery that the consumer can readily insert into and remove from a reusable housing. The power supply needs to be lightweight, volume efficient and easily adaptable to a wide array of cell phones that utilize batteries of various shapes and sizes.